Enhancing methane oxidation in a bioelectrochemical membrane reactor using a soluble electron mediator
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Biotechnology for Biofuels Open Access
RESEARCH
Enhancing methane oxidation in a bioelectrochemical membrane reactor using a soluble electron mediator Xueqin Zhang1 , Hesamoddin Rabiee1, Joshua Frank1, Chen Cai1, Terra Stark2,3, Bernardino Virdis1, Zhiguo Yuan1 and Shihu Hu1*
Abstract Background: Bioelectrochemical methane oxidation catalysed by anaerobic methanotrophic archaea (ANME) is constrained by limited methane bioavailability as well as by slow kinetics of extracellular electron transfer (EET) of ANME. In this study, we tested a combination of two strategies to improve the performance of methane-driven bioelectrochemical systems that includes (1) the use of hollow fibre membranes (HFMs) for efficient methane delivery to the ANME organisms and (2) the amendment of ferricyanide, an effective soluble redox mediator, to the liquid medium to enable electrochemical bridging between the ANME organisms and the anode, as well as to promote EET kinetics of ANME. Results: The combined use of HFMs and the soluble mediator increased the performance of ANME-based bioelectrochemical methane oxidation, enabling the delivery of up to 196 mA m−2, thereby outperforming the control system by 244 times when HFMs were pressurized at 1.6 bar. Conclusions: Improving methane delivery and EET are critical to enhance the performance of bioelectrochemical methane oxidation. This work demonstrates that by process engineering optimization, energy recovery from methane through its direct oxidation at relevant rates is feasible. Keywords: Bioelectrochemical membrane reactor, Redox mediator, Bioelectrochemical methane oxidation, ANME, Ferricyanide Background Methane (CH4) is an important energy resource that has attracted increasing attention due to rapidly growing energy demand. C H4 resource is abundant with two sources: fossil natural gas with growing proven reserves, and biogas with renewable availability [1, 2]. Thus CH4 provides us a long-term energy sustainability. Moreover, CH4 is also recognized as a potent greenhouse gas
*Correspondence: [email protected] 1 Advanced Water Management Centre, Faculty of Engineering, Architecture and Information Technology, The University of Queensland, Brisbane 4072, Australia Full list of author information is available at the end of the article
(GHG), with its global-warming potential 28–34 times that of carbon dioxide over a 100-year time frame [3]. It is therefore desirable for direct C H4 utilization or upgrading on-site to minimize its global-warming potential. Both factors sparked interests on developing effective CH4-based technologies to produce energy whilst mitigating its adverse impact on climate change [4, 5]. While direct CH4 combustion in gas turbines has been a widely implemented strategy for energy recovery from CH4, this approach is constrained by the inherently low volumetric energy density for transportation sector and low energy efficiency for electricity generation [6]. Proposed alternatives for CH4 utilization include direct CH4 conversion into electric
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